1. Touch with natives
Engine way:
PHP Code:
#include <amxmodx>
#include <amxmisc>
#include <engine>


public plugin_init() {
    register_plugin("Touch Test","0.1","SAMURAI");
    
    // now registers a touch action to a function. 
    register_touch("touched","toucher","hook_touch"); 
}


public hook_touch(touched,toucher)
{
    if(is_user_admin(toucher) && is_user_bot(touched))    
    {
        client_print(0,print_chat,"kbooom")
    }
    
} 

touched = Who are touched by Toucher
toucher = Who touch

If you want to filter touched / toucher
An example :
Only running hook_touch if a player touch something..
PHP Code:
register_touch("player","*","hook_touch"); 


2. Forwards touch:
Engine way:
PHP Code:
#include <amxmodx>
#include <amxmisc>
#include <engine>


public plugin_init() {
    register_plugin("Touch test","0.1","SAMURAI");
    
    
}

// Called when two entities touch/collide. 
public pfn_touch(ptr,ptd)
{
    new classname[32]
    entity_get_string(ptr,EV_SZ_classname,classname,31) 

    
    if ( equal(classname, "hostage_entity") ) 
    {
        client_print(0,print_chat,"damn touched");
        // and other stuff
    }
} 



Fakemeta way:
PHP Code:
#include <amxmodx>
#include <fakemeta>

public plugin_init() {
    register_plugin("Touch Test","0.1","SAMURAI");
    
    register_forward(FM_Touch,"hook_touch");
}

public hook_touch(ptr,ptd)
{
    new classname[32]
    pev(ptr,pev_classname,classname,31)
    
    
    if ( equal(classname, "hostage_entity") ) 
    {
        client_print(0,print_chat,"damn touched");
        // and other stuff
    }
    
} 


3. Block touch operation:
On Engine:
To block touch use return PLUGIN_HANDLED;

On Fakemeta:
use return FMRES_SUPERCEDE;

4. Fake Touch:
This will simulates two entities colliding/touching.
Engine:
PHP Code:
fake_touch(Touched,Toucher) 
Fakemeta:
PHP Code:
dllfunc(DLLFunc_Touch, touched, toucher)